The role of 18F-fluorodeoxyglucose positron emission tomography in differentiated thyroid cancer before surgery

Abstract

The incidence of thyroid cancer in both men and women is increasing faster than that of any other cancer. Although positron emission tomography (PET) using 18 F-fluorodeoxyglucose (FDG) has received much attention, the use of FDG PET for the management of thyroid cancer is limited primarily to postoperative follow-up. However, it might have a role in selected, more aggressive pathologies, and so patients at a high risk of distant metastasis may benefit from PET before surgery. As less FDG-avid thyroid cancers may lower the diagnostic accuracy of PET in preoperative assessment, an understanding of FDG avidity is important for the evaluation of thyroid cancer. FDG avidity has been shown to be associated with tumor size, lymph node metastasis, and glucose transporter expression and differentiation. As PET is commonly used in clinical practice, the detection of incidentalomas by PET is increasing. However, incidentalomas detected by PET have a high risk of malignancy. Clinicians handling cytologically indeterminate nodules face a dilemma regarding a procedure for a definitive diagnosis, usually lobectomy. With 'nondiagnostic (ND)' fine-needle biopsy (FNA), PET has shown a negative predictive value (NPV) of 100%, which indicates that negative uptake in a ND FNA procedure accurately excludes malignancy. With 'atypia of undetermined significance' or 'follicular neoplasm', the sensitivity and NPV of PET are 84 and 88%. PET does not provide additional information for the preoperative assessment of thyroid cancer. However, factors associated with FDG positivity are related to a poor prognosis; therefore, FDG PET scans before surgery may facilitate the prediction of the prognosis of differentiated thyroid cancer.

IMAGING IN ENDOCRINOLOGY: 2-[18F]-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography in differentiated thyroid carcinoma: clinical indications and controversies in diagnosis and follow-up

“…Although there were some false-positive cases, more than half of the patients (108/197) were spared unnecessary surgery after PET. Similar cumulative results were recently reported in a review by Pak et al (67). When an FDG-PET scan with a nodule uptake that was higher than the normal thyroid background was considered positive, the cumulative sensitivity, specificity, PPV and NPV of FDG-PET in detecting malignancy were 84, 52, 43, and 88% respectively.…”

“…Although FDG-PET/CT is used in the pre-surgical management of DTC, its routine preoperative use is usually considered inappropriate (20). On the contrary, FDG-PET/CT is widely used in the postoperative follow-up of DTC, mainly after RAI ablation in patients with elevated serum thyroglobulin (Tg) levels but negative WBS (5).…”

Feasibility of FDG-PET/CT for the initial diagnosis of papillary thyroid cancer

“…Jeong et al [14] recently reported that the standardized uptake value (SUV) of PTMCs did not correlate with the presence of lymphatic metastasis, multiplicity of the primary tumor, or extrathyroid extension (ETE) but correlated only with the size of the PTMCs. On the other hand, other study groups have shown a significant association between FDG uptake and aggressive histological features [15], tumor size, and lymph node metastases [10,16].…”

Differentiated thyroid cancer incidentally detected by 18F-FDG PET/CT: patient’s future in a hot-spot?

“…18 F-FDG uptake by the primary DTC has also been linked with aggressive histological features, tumour size and lymph node metastases [10,11]. In their analysis, Piccardo and colleagues have taken a step forward on these prognostic issues as they linked 18 F-FDG intensity of the thyroid hot-spot which resulted in the discovery of DTC with the future of the patients.…”